Hand impairment is a common condition that contributes substantially to disability in the U.S. and around the world. In the case of stroke alone, it is estimated that 80% of the 700,000 individuals who survive a stroke each year require hand therapy. Intensive rehabilitation exercise reduces long-term hand impairment. Unfortunately, as soon as 2 weeks after the onset of an injury, people often must perform hand therapy at home without professional assistance. Individuals rarely comply with written home programs for home therapy. To address this problem, we have developed the MusicGlove, an affordable instrumented glove that requires the user to practice functional gripping movements to play a custom computer game inspired by the third most popular video game in gaming history, Guitar Hero. In our Phase I study with 16 individuals with a stroke who used the device at home, and an earlier pilot study with 9 individuals with a stroke who used the device in the clinic, we found that the MusicGlove accurately measures clinical hand impairment level, inspires people to make over 1400 practice grip movements in 40 minute training sessions, and stimulates significantly greater improvements in hand function than conventional therapy. Our aims for Phase II are to: 1) Develop a production model of the MusicGlove suitable for commercialization (months 1-12). We will modify our functional prototype to be robust, easy to use, and efficiently manufactured in an FDA-compliant way, and will complete development of an intuitive, easy-to-use game interface that automatically quantifies and logs the user's movement and use habits. We will also develop next generation technologies for improved future models. 2) Perform a two-site randomized controlled trial of the device with sub-acute stroke patients (months 12-24). Individuals with subacute stroke are a large potential user group. At two sites, we will randomize 44 individuals with a subacute stroke to receive additional therapy with the MusicGlove or additional conventional therapy for four weeks. We hypothesize that the individuals who exercise with the MusicGlove will improve their Box & Block score by a clinically significant amount (6 blocks), compared to the control group. 3) Conduct a pilot study of use of the device with individuals with a chronic, cervical, incomplete SCI (months 12-24). We will also establish initial safety, feasibility, and efficacy for individuals with a SCI (n = 20), another important user group 4) Solicit feedback on usability of the device in normal clinical practice (months 12-24). We will distribute the MusicGlove to three leading rehabilitation units, and study how these units incorporate the device into their patient care. This Phase II project will result in a commercially- ready, clinically-validated product that we will produce and sell.